An important feature of any acoustic system is the transducer. A transducer typically incorporates an electro-acoustic element which converts electrical signals into mechanical vibrations in the transmit mode and mechanical vibrations into electrical signals in the receive mode. There are many factors that influence the behavior of a transducer, including the choice of material, physical dimensions, electrical connection, mechanical construction, the external load conditions and the capacity to dissipate heat.
Ceramic cylinders frequently constitute the electro-acoustic element in underwater acoustic transducers and may be either tangentially poled or radially poled. Tangentially poled cylinders provide higher electro-mechanical coupling than radially poled cylinders, making them the preferred choice for many high-power, broadband applications. Tangentially poled cylinders have striped electrodes and operate in the k33 mode (i.e. the direction of the electric field is the same as the direction of the dielectric displacement). Radially poled cylinders have an electrically conductive plating on the outer and inner surfaces and operate in the k31 mode (i.e. the direction of the electric field is orthogonal to the direction of the dielectric displacement).
One particularly common problem with transducer construction is the difficulty of creating a reliable method of making the electrical connection to the electrodes. The conventional way of connecting to the electrodes on ceramic is to use soldered wire. On tangentially poled cylinders this entails soldering daisy-chained wire to alternate striped electrodes while on radially poled cylinders, wire is soldered to the inner and outer surfaces.
One of the problems with this method is that the solder joint is an unreliable connection, subject to failure during either handling or actual operation. This inherent unreliability of the solder joint originates in the soldering process. When solder is applied to one end of a wire, expansion occurs. Then the solder solidifies and as the wire cools it contracts. If additional wire length is not left to compensate for the heating and subsequent cooling, the wire will stretch and generate stress in both the wire and the solder joint. In small tangentially poled ceramic cylinders, the close proximity of the solder connections makes it difficult to leave adequate wire length in the daisy chain to relieve the process-induced stress.
Besides being unreliable, the soldering process is also labor intensive. This is especially true in tangentially poled cylinders with a large number of striped electrodes.
Additional problems with the solder connections occur in high frequency, high power applications. The large acceleration force on the solder joint causes the wire to flex. This can result in mechanical fatigue and wire fracture. The fractured joint could then induce arcing, resulting in catastrophic failure.
Therefore, there is a need for an approach which controls wire flexing in ceramic cylinders using solder joints or eliminates the need for soldering wires to the ceramic altogether. There is also a need for a standardized process that reduces human intervention in transducer manufacture. In addition, there is a need to provide design simplicity, reliability, and reduced labor costs along with improved heat transfer from the ceramic cylinders.